1. Field of the Invention
The present general inventive concept relates to a timing controller, and more particularly, to a timing controller to change a data inversion method based on an image pattern of data in a display device.
2. Description of the Related Art
When a representative flat panel display device such as a thin film transistor liquid crystal display (TFT-LCD) panel, is driven, an alternating current (AC) driving method is used in order to prevent the degradation of the panel.
FIG. 1 illustrates a unit pixel in a conventional TFT-LCD panel. Referring to FIG. 1, the unit pixel includes a transistor Tr, a liquid crystal capacitor Clc, a storage capacitor Cst, and a parasitic capacitor Cgd between a drain and a gate of the transistor Tr.
In the AC driving method, a common voltage VCOM needs to be maintained constant in order to represent the same grayscale value. However, an offset component occurs in the common voltage VCOM due to the parasitic capacitor Cgd. This phenomenon is referred to as a kick-back effect. A flicker occurs due to the offset component in the common voltage VCOM. At this time, if an image pattern which is the same as that in a data inversion method in the display device is input, the kick-back effect is increased, and therefore, the flicker becomes worse.
FIG. 2 illustrates waveforms of a plurality of signals used to drive the unit pixel illustrated in FIG. 1. A procedure in which a flicker occurs due to an offset component Voffset in the common voltage VCOM will be described with reference to FIGS. 1 and 2.
A gate voltage VG is applied to turn on the transistor Tr and a drain voltage VD is a drain voltage of the transistor Tr. It is ideal that the common voltage VCOM maintains constant, but the offset component Voffset occurs due to the kick-back effect caused by the parasitic capacitor Cgd.
The voltage that is applied to both ends of the liquid crystal capacitor Clc in order to drive the unit pixel must be a voltage between the drain voltage VD and the common voltage VCOM′ having the offset component Voffset. Referring to FIG. 2, a driving voltage for an odd frame and a driving voltage for an even frame are asymmetric with respect to the common voltage VCOM not having the offset component Voffset. Accordingly, a voltage applied to both ends of the liquid crystal capacitor Clc with respect to the odd frame is different from that with respect to the even frame. As a result, the brightness of the unit pixel is different, causing a flicker.
At present, panel manufacturers produce panels for which an offset voltage of a common voltage has been compensated for using variable resistance. However, since the offset voltage of the common voltage changes according to a type of panel and the position of a pixel, it is difficult to accomplish exact compensation.